As people become more mobile, the number of portable devices, e.g., notebook computers, personal data assistants, cell phones, etc., continues to increase. The use of wireless communications techniques enables modern portable devices to receive and transmit data from various locations.
With recent advances in the Internet and other data services, users of portable devices are beginning to feel a need to receive and transmit ever increasing amounts of data using wireless communications techniques.
In wireless communications a data signal, e.g., a series of symbols, is frequently modulated on a carrier signal, e.g., a carrier tone, having a particular carrier or tone frequency. In order to increase the amount of data that can be transmitted in a given period of time, a plurality of different carriers may be used to transmit data, e.g., symbols, in parallel. This results in the broadcasting of what is known as a multi-tone signal. When multi-tone signals are used, the bandwidth of the system becomes a function of the number of carrier signals in the multi-tone signal. An OFDM signal is one particular type of multi-tone signal.
As the result of the transmission of a signal through a communications channel and the processing of the received signal, e.g., by a tuner and other circuitry, the transmitted signal may be distorted. For example, the communications channel may introduce amplitude and/or phase distortions. Tuners and other receiver circuitry may introduce time varying phase distortions sometimes call phase jitter. Such signal distortions can make it difficult to recover transmitted data, e.g., symbols, from a received signal.
Communications channel distortions are difficult to avoid particularly in the case of over the air transmissions. Accordingly, attempts at addressing communications channel distortions have focused primarily on compensating for the introduced distortions at some point in the receiver.
Phase jitter, in contrast to communications channel distortions, can be reduced or eliminated by using high quality circuits in the receiver. Accordingly, attempts at addressing phase jitter have been focused on using better quality tuners and other circuits in a receiver than those which introduce unacceptable amounts of phase jitter.
While reducing phase jitter by using high quality receiver components can be effective, it has the disadvantage of requiring the use of high quality components which are usually more expensive than lower quality components, i.e., the components which introduce more phase jitter. In consumer applications, cost is often a major concern. Accordingly, from a cost perspective, in many applications the use of high quality tuners and other comparatively expensive circuitry can be undesirable.
In view of the above discussion, it should be apparent that there is a need for methods and apparatus for increasing the amount of phase jitter which can be tolerated in a receiver, e.g., a multi-tone signal receiver, thereby facilitating the use of relatively inexpensive tuners and/or other receiver circuitry. In addition, from a cost perspective, it is desirable that at least some methods and apparatus for enhancing a receiver's tolerance of phase jitter be relatively straight forward and inexpensive to implement.